Methods for producing L-amino acids from N-acyl-D,L-amino acids have been known in the art (see, for example, Japanese Patent Application Laid-Open (Kokai) No. 22188/88).
However, the deacyl enzymes reported previously show a weak activity in deacylating N-acylated compounds of phosphorus-containing amino acids or acidic amino acids.
L-2-amino-4-hydroxy(methyl)phosphinylbutyric acid represented by the formula (III): ##STR4## which is one target compound of the invention, is a compound useful as a herbicide named Glufosinate (common name). Racemic 2-amino-4-hydroxy(methyl)phosphinylbutyric acid is currently used for the purpose. Actually, only the L-isomer shows the herbicidal activity. Thus, it has been desired to develop a method capable of producing potent L-2-amino-4-hydroxy(methyl)phosphinylbutyric acid selectively and inexpensively.
In recent years, there have been required those agricultural chemicals which are not only highly potent as pesticides but also mild to the environment. For decreasing the influence upon the environment, it is desirable not to release inactive isomers into the environment at use of the agricultural chemicals.
A fermentation method is known to produce L-2-amino-4-hydroxy(methyl)phosphinylbutyric acid, but is expensive.
As for enzymatic production of L-2-amino-4-hydroxy-(methyl)phosphinylbutyric acid from N-acyl-D,L-2-amino-4-hydroxy(methyl)phosphinylbutyric acid, there have been reported to date only the following two methods, a method using cells of microorganisms belonging to the genus Pseudomonas, Streptomyces or Aspergillus (Japanese Patent Application Laid-Open No. 47630/80) and a method using penicillin G-acylase (Japanese Patent Application Laid-Open Nos. 138394/82 and 51099/89).
However, L-2-amino-4-hydroxy(methyl)phosphinyl-butyric acid obtained by the former method shows an optical rotation of 23.degree. (C=1, 1N HCl) at the maximum, the optical purity being low (ca. 75%) (Japanese Patent Application Laid-Open No. 51099/89). Also, the working temperature of the enzymes is in the range of 28.degree. to 35.degree. C. and the inactivation occurs at 50.degree. C. (Japanese Patent Application Laid-Open No. 47630/80). Thus, the method is not practical for industrial production. In addition, they show only a weak action or no action at all on the acylated compounds of L-amino acids other than N-acyl-L-2-amino-4-hydroxy(methyl)-phosphinylbutyric acids (Japanese Patent Application Laid-Open No. 47630/80).
It is also known that conventional aminoacylase is quite inactive to the acyl group of N-acyl-D,L-2-amino-4-hydroxy(methyl)phosphinylbutyric acids (Japanese Patent Application Laid-Open No. 138394/82).
On the other hand, the latter method using penicillin G-acylase is not practical because a phenacyl group is used as an eliminating group.